Four Humours: This was an ancient idea, first put forward by Hippocrates. The universe is made up of four elements; and the body is made up of four humours, blood, phlegm, yellow bile, black bile. If these humours are in balance the body will be healthy, when they are unbalanced you become ill. Galen developed the idea with theory of Opposites. For example, f you had a phlegmy cold, this should be balanced by eating something hot eg pepper.